Torquetum

3-D Printable Torquetum 

By Jeff Williams

Inspired by Seb Falk’s The Light Ages.

Adapted from an article by Richard A. Paselk, and images found at various virtual museums found across the internet.

A torquetum is a medieval era observing and calculating device. Many of the originals were works of art as much as advanced scientific instruments and mathematical mechanical computers. The torquetum allowed the observer to measure a star’s or planet’s location in one of three different coordinate systems. One is the observer's point of view relative to the horizon (both parts closed), the second is relative to the earth’s equator (Tabula Equinoctialis is set to the observer’s latitude), and the third is relative to the planetary ecliptic (Tabula Equinoctialis is set to the observer’s latitude and the Tabula Orbis Signorum is propped up with the Stilus). It seems excessively complicated to use to make measurements and is probably more useful as an analog computer for converting measurements made by other devices to one of the other coordinate systems without doing the spherical trigonometry.

Some of the adaptions allow for 3-D printing such as raised lettering and markings so that the top couple of layers can be printed in a different color by pausing the print and changing filaments. Other changes have been made to accommodate the FDM process and to minimize printing supports. The scale on the Tabula Orizontis has been extended to range from a latitude of 9° N to 90° N as I live considerably further south compared to those who designed and built the originals in Medieval Europe.

This is rather large and will not fit on many print beds. Will fit on something like a Prusa XL if you split the Tabula Orizontis (the base). I printed this on a Prusa i3 MK 3S+ by scaling each part by 70%. I still had to split the base piece. I used PLA, a 0.4mm nozzle with a layer height of 0.2 mm. A larger nozzle or layer height may lose some detail on the markings and symbols. All of the parts can be printed in PLA. 2 perimeters and 15% infill should work fine. I found using at lest 4 layers for the top gave a fairly flat and smooth surface. When assembling, do not tighten the fasteners to tight. The various parts should move freely except for the hour circle. Ny-lock nuts may be helpful. The only fasteners that should be tight enough to restrict movement are the two on the protractors of the Tabula Orizontis. Once this is set for your latitude, it should not need to change unless you relocate the device. The Crista has a triangular protrusion that fits into a corresponding notch in the Turnus. Normally these two parts would be a single piece.

Note the dimensions are optimized for a full size print. Scaling down will lose some detail in the text. A 0.25 mm nozzle may be necessary to get the best result with the scaled down version. Someday I hope to get a larger format printer and make this full size. 

If you find any errors, please let me know. Information is scarce as there are few in existence.

Detailed construction instruction are in the included pdf.

Bill of Materials: